London, UK to Praslin Island is an approximately 15-hour flight. You can also do a combination of flight, car, and ferry; or do a combination of train, bus, and flight. Due to the time zone difference, you'll lose 4 hours traveling from London to Praslin Island. Traveling from London in December, things will get much hotter in Praslin Island: highs are around 36°C and lows about 28°C. Cap off your sightseeing on the 17th (Mon) early enough to catch the ferry to La Digue Island.

Traveling by combination of ferry, car, and flight from La Digue Island to Mumbai takes 8.5 hours. Alternatively, you can do a combination of ferry and flight. The time zone difference when traveling from La Digue Island to Mumbai is 1 hour. Expect slightly colder evenings in Mumbai when traveling from La Digue Island in December, with lows around 20°C. Finish up your sightseeing early on the 20th (Thu) so you can travel back home.